It is well known that the use of a turbocharger can increase the efficiency of an internal combustion engine by using the exhaust pressure to power a turbine, which in turn drives a compressor that boosts the pressure of the intake air.
Early turbochargers, however, often provided only an insignificant boost of the intake air pressure at low RPMs, and exhibited a significant so-called turbo lag (the time required to change power output in response to a throttle change).
One approach to expand the operating range (in RPMs) across which a significant boost is provided, is to use a so-called twin scroll turbocharger, in which exhaust gases are guided to the turbine wheel of the turbocharger through two separate scrolls. This approach enables a reduced minimum cross-sectional area of the flow channel between combustion chamber(s) and turbine wheel, which in turn provides for a relatively high flow speed of exhaust gas to the turbine wheel also at low RPMs.
For improving the turbo response (reduce the turbo lag), it has been proposed to provide pressurized air to the turbine of the turbocharger. For example, DE 10 2010 053 057 discloses a turbocharger device in which pressurized air is provided to the turbine from a storage container to quickly increase the rotation of the turbine wheel.
Although the turbocharger according to DE 10 2010 053 057 appears to be capable of reducing the turbo lag, it would be desirable to provide for a further reduction in the turbo lag and/or a more energy efficient way of reducing the turbo lag.